In battery-driven vehicles, it is important to know the state of the battery. This includes measuring the supply or terminal voltage.
The voltage measurement takes place via an ohmic voltage divider having a downstream A/D converter. The challenge lies in the requirement that the battery is loaded with a current that is >10 μA in the power-off state. One way to solve this is to connect an opto-MOSFET in series in order to disconnect the voltage divider from the battery. In addition, the voltage divider ratio increases with increasing battery voltage. This means that at high voltages, the voltage divider ratio must be extremely high, for example, 1000 to 1. For this purpose, many high-resistance resistors are connected in series, which is expensive.